1. Field of the Invention
The present invention relates to a half mirror used in a decorative panel of an electronic device, and more specifically, to an art for preventing the deterioration of appearance of the half mirror caused by a vapor deposited layer of the half mirror being burned by static electricity charged in the half mirror.
2. Description of the Related Art
Heretofore, a half mirror used as a decorative panel disposed on a front face of an electronic device is equipped with a metallic electric conductor functioning as earth to prevent static electricity from being charged in the half mirror. However, to prevent the half mirror from being damaged (scratched) by the hard metallic conductor being in direct contact therewith, it is popular to provide a narrow gap therebetween to create a pseudo-connection. However, if the gap is too narrow, the half mirror may still be scratched, but if the gap is too wide, the potential of the static electricity being charged in the half mirror increases, by which the energy of discharge to the metallic conductor becomes too strong, causing even greater burn of the vapor deposited layer of the half mirror and deteriorating the quality of the half mirror as decorative panel.
Japanese Patent Application Laid-Open Publication No. 2003-185815 (patent document 1) discloses one example of such an electronic device. Patent document 1 discloses, as illustrated in FIG. 6, an art of adhering a metallic tape 60 with a conductive paste 32 on a vapor deposited layer 21 of a half mirror 20, and arranging a conductive member 61 between a conductive chassis 40, thereby conducting the static electricity charged in the half mirror 20 via the metallic tape 60 and the conductive member 61 to the conductive chassis 40. Further, a method is disclosed to realize conduction by having the conductive member 61 connected to the conductive chassis 40 come in contact with the vapor deposited layer 21 of the half mirror 20, as illustrated in FIG. 7.
According to the prior art disclosed above, a metallic conductor is used as an earth to prevent static electricity from being charged in the half mirror used in the decorative panel on the front face of an electronic device, but a narrow gap is provided therebetween to realize pseudo-connection, so as to prevent the hard metallic conductor from damaging the hard mirror through direct connection. However, if the gap is too narrow, the half mirror may still be damaged, and if the gap is too wide, the potential of the static electricity being charged in the half mirror increases, by which the energy of discharge to the metallic conductor becomes too strong, causing even further burn of the vapor deposited layer of the half mirror and deteriorating the quality of the half mirror as the decorative panel. Therefore, the size of the metallic conductor must be strictly managed in order to reduce the variation in the size of the gap (distance) created between the vapor deposited layer of the half mirror and the metallic conductor. Moreover, the metallic conductor disposed near the vapor deposited layer of the half mirror must have very small surface roughness, and the assembling of the conductor must be carried out carefully so as not to create any scratches or bumps on the vapor deposited surface of the half mirror.
Moreover, as shown in FIG. 6, patent document 1 discloses a half mirror having a metallic tape 60 with conductive paste attached to a vapor deposited layer 21 of the half mirror, and further having a conductive member 60 disposed between the conductive chassis 40, to thereby conduct the static electricity charged in the half mirror 20 via the metallic tape 60 and the conductive member 61 to the conductive chassis 40. According to this technique, the half mirror 20 and the conductive chassis 40 are not directly connected by the metallic tape 60, but with a conductive member 61 additionally disposed. Therefore, the position for adhering the metallic tape 60 is restricted to the location in which the conductive member 61 is positioned between the conductive chassis 40 and the half mirror 20, which is a difficult condition to fulfill considering the arrangement of components in recent electronic devices having minimum capacity inside the electronic devices. Furthermore, a very strict accuracy in size is required to maintain a constant connection through the arrangement of the half mirror 20, the metallic tape 60 and the conductive member 61, and very careful assembly work is required in assembling the electronic device, by which the work efficiency is deteriorated. On the other hand, as illustrated in FIG. 7, a method is disclosed for realizing conduction by having a conductive member 61 in contact with the conductive chassis 40 being in direct contact with the vapor deposited layer 21 of the half mirror 20, but it is disclosed in the patent document that this arrangement requires means to prevent the vapor deposited layer from being scratched by the conductive member, such as by specially designing the shape of the conductive member.